Treatment of synthetic textile fibers



Jan. 18, 1944. 1'. A. FEILD, JR 2,339,323

- TREATMENT OF SYNTHETIC TEXTILE FIBERS I Filed Apx il 22, 1939 2 Sheets-Sheet 1 INVENTOR THEOPHILUS A. FEILD, JR.

ATTORNEY PERCENT SHRINKAGE AND ELONGATION 3m 13, 1944. T A. FEILD, R 2,339,323

TREATMENT OF SYNTHETIC TEXTILE FIBERS Filed April 22, 1959 Z SheetS-Sheet ATTORNEY 'to produce a commercially Patented Jan. 18, 1944 was... A. Feild, In. Charleston, wl va. is.

. signer to Carbide and Carbon Chimicals Cor-pa.

ration, a corporation of New Yer Application April 22, 1939, Serial No. 269,446 8 Claims. (01. 6-1155) This invention relates to the art of treating artificial textile flbers, and it is particularly directed to the processing of fibers and yarnsmade from vinyl resins, continuously and on a commercial scale.

Of these, the invention is especially directed to the processing of filaments made from the vinyl ester resins which may result from the conjoint polymerization of vinyl halides with vinyl esters of aliphatic acids, preferably containing between about 70% and about 95% by weight of the vinyl halide in the polymer and having high. average macromolecular weights, preferably in excess of 15,000. Molecular weights referred to herein are those calculated by means of Staudinger's formula from viscosity determinations of solutions of the resins. Those resins are especially preferred which are made by the conjoint polymerization of vinyl chloride with vinyl acetate.

The preparation of filaments from the resins resulting from the conjoint polymerization of vinyl halides with vinyl esters of aliphatic acids is described in United States Patent No. 2,161,766, issued June 6, 1939, to E. W. Rugeley, T. A. Feild,

, Jr., and J. ,F. Conlon, withwhich this application contains material in common.

After the resin has been extruded, or spun, into filaments, and made into yarn, it is desirable to increase the strength of the yarn by stretching. In the case of the vinyl resin fibers described, which are highly elastic, it is necessary to "set" the-stretch in the yarn made therefrom, or else the yarn will contract upon being unwound from the bobbin. The setting treatment may comprise a ing the yarn for a period or time under tension or subjecting it to elevated temperatures below its softening point (that is, the highest temperature to which the yarn may be subjected without altering its filamentary character) either dry or-submerged in a liquid medium which will not attack or alter the yarn. Since yarns of this type often become still when subjected to elevated temperatures below their softening points for relativelylong periods of time, this hardness of texture must be removed in order desirable textile. This may be accomplished by "flexing" the yarn or passing it over rollers or guides of small diameter at fairly high speeds.

Ordinarily, the setting," or stabilizing, treatment has been accomplished by immersing the stretched yarn in a heated water bath while under tension on the bobbins. Thi bobbin set-,

the yarn quite still on the inside portion of the yarn cake and relatively soft on the outside. Since the setting treatment, which is for the l purpose of reducing the shrinkage of the stretched filaments by relieving internal strains, also produces changes in the tenacity and elongation characteri tics of the yarn, it is important that the setting operation should not uniformly upon all of the yarn in process and also be amenable to close control.

This invention. provides a methodof setting the yarn continuously as it is, wound from one ture at which the setting takes bobbin t another, and at thesame time flexing the ya to give it a uniformly soft feel. The yarn so processed is characterized by its very uniform tenacity, elongation and lustre because this method of setting and flexing the yarn continuously as it comes from the stretching machine, or from bobbins wound under tension, permits of very close control both of the temperaplace and of the exposure of the yarn thereto.

The process of this invention generally comprises transferring the yarn from a supply spool by continuously passing the yarn around a large friction roll positively driven to hold the yarn under sufllcicnt tensionto maintain the required degree of stretch, then flexing the yarn into a curve of small radius, as by passing it around one or more small diameter idler rollers, then carrying the yarn back to the friction roll, usually making several laps between the friction roll and the idler rolls, and finally onto a take-up ting" method has the disadvantage that it leaves 66 spool. This assembly of rollers is maintained in a fluid medium at a predetermined, constant, elevated temperature to set the stretched yarn. Although the heating medium may be a heated gas or vapor, the more practicable method is to submerge the rollers, at least partially, in a heated liquid bath, such as water. The small diameter rollers flex the yarn as it passes over them.

In the drawings, Fig. 1 is a diagrammatic representation of a typical method of practicing the invention, and Fig. 2 is a chart showing typical characteristics obtainable in yarn made from fibers of the. vinyl resins described when treated in accordance with the invention. Referring to Fig. 1, the stretched but otherwise untreated yarn in may be supplied directly from the stretching apparatus, or, as shown. wound on a bobbin II. The bobbin II is (rictionally driven by means of a feed roller I: so that the yarn is metered oil at a constant rate. From the bobbin II the yarn it passes to and around a roller l3 and around the flexing roller.

ripheral speed as the feed roller 12. The yamis wound evenly upon the bobbin It by means of a traverse mechanism l1 throughwhich the yarn passes just before it reaches the bobbin 15. The roller l3, which is preferably also positively driven at the same peripheral speed as rollers l2 and I0, is partly submerged in a liquid medium, such as water, in a tank l8 which is maintained at the desired setting temperature.

In the continuous process of setting and simultaneously flexing the stretched yarn, as described above, it is necessary to correlate the setting temperature with the time of exposure thereto and the percentage stretch of the yarn resulting from the stretching operation; in order to obtain a yarn having the greatest strength, resiliency and elasticity. The effect of the setting treatment may be considered as the relieving of the strains set up in the yarn during the stretching operation sufliciently to prevent the thread from shrinking at room temperature and restrict shrinkage at higher temperatures. Relieving the strains by heat to produce uniform shrinkage characteristics also results in an alteration of the'tenacity and elongation characteristics of the yarn. The. tenacity and shrinkage characteristics vary directly with each other,

and both reach a more or less constant value for each setting temperature. That is, the longer the period of setting and the higher the temperature, the lower the tenacity becomes and the less will the yarn shrink at room or higher temperatures upon release of the tension applied while and shrinkage characteristics areindicated in and set at three different temperatures, namely, 80, 90 and 93 C., for different periods of time ranging up to seven seconds. Tests were made to determine the elongation, shrinkage and tenacity characteristics of these variously treated samples of yarn The results of these tests form the basis for the dotted curves of Fig. 2. Different exposure periods were obtained by varying thenumber of thread laps around the flexing rollers 14 and the roller l3, shown in Fig. 1. One thread lap was equivalent to 0.21 second exposure. Strength (tenacity) and elongation characteristics of the finished yarn were determined by the conventional manner. The test for yarn in water at65" C. for 30 minutes and measuring the resulting change in length. The elongation percent, and the tenacity in grams per denier, for various periods of exposure in the setting treatment.- The stretch was maintained during setting as described with reference to the apparatus shown diagrammatically in Fig. 1. The dotted. curves indicate the tenacity, elongation and shrinkage characteristics, and are designed by the letters T, E and S, respectively. Along with these letters, on each curve, are given both the temperature of setting in degrees centigrade and the percent to which the yarn was stretched prior to the setting treatment. The shrinkage curve for the yarn stretched 140.5% and set at 90 C. is omitted, because it very nearly coincides with the shrinkage curve for the yarn stretched 186% and set at 93C.

The denier and number of filaments of the yarn being processed has some effect upon the results when employing a liquid setting bath. As a rule, the fine denier yarns are slower and more difiicult to set than the larger sizes. This may be due to the fact that different yarn sizes carry Y different amounts of hot water from the setting However, for a given amount of stretch at a given temperature, the tenacity and shrinkage become more or less constant with each setting temperature, as the time of exposure of the yarn is increased. The elongation characteristics of the yarn increase more or less steadily as the time of exposure to the settin temperature is prolonged. 'At higher temperatures of setting, or stabilizing, with longer periods of exposure, the yarn beco'mesmore lustrous and stiffer. Increasing the temperature at which the yarn is stretched generally permits a reduction in the amount of setting," or stabilizing, that is needed. Suitable control of these factors permits the production of yarn with practically any desired finish.

Fig. 2 is a chart indicating the results obtainable under different conditions of stretching and setting with a typical vinyl resin yarn spun from a conjoint polymer of vinyl chloride with vinyl acetate, having about 87% vinyl chloride in the polymer and a macromolecular weight in excess of 15,000. Referring to the dotted curves, the' test yarn was composed of 240 filaments, one deier each, which was twisted 9.5 turns per inch. One part of this yarn was then stretched 140.5% andanother part was stretched 186%, while at a temperature between 93 and 94C. Samples of each of these two lots of yarn were then flexed bath, the lighter yarns carrying less, with a resultant loss in effective exposure to the setting temperature. The solid curves in Fig. 2 indicate the tenacity, elongation and shrinkage characteristics of yarn of the same composition as that employed in determining the dotted curves, but of 240 and filaments, both stretched 186 and set at a temperature of 85 0. As is the case with the dotted curves, the tenacity, elongation I and shrinkage curves are indicated by the letters u 93-E-186% yarn stretched 186% and set T, E and S, respectively, and the number accompanying the letter on each curve represents the number of one denierfilaments composing the yarn. 1' The curves of Fig. 2 may be tabulated as fol ows:

(T) Tenacity in grams per denier at C.

240-T yarn of 240 denier stretched 186% and set (E) Percent elongation -E-140.5% yarn stretched 140.5% and set at assasss 240-1 tern of 240 denier stretched 186% and set at 85 C. 60-1: yarn of 60 denier stretched'lattt and set (S) Percent shrinkage so-s-1ac% yarn stretched 188% and set at aoc.-

-9s=-s-1ac% yarn stretched 186% and set at 80-8 yarn of 60 denier stretched 188% and set at 86 C.

240-8 yarn of 240 denier stretched 188% and set at 85 C.

The yarn, thread, or filaments, of vinyl resin must be stretched and set .in the absence of a' solvent in order to impart a substantial increase in strength, and, or course,-if thesetting medium is a liquid, it must be one which willnot appreciably attack or swell the yarns or individual fibers or soften them by impregnation. If it is desired to set the fibers at temperatures above 100 0., other liquids, such as mineral oil and the various glycols, may be used in place of water, and if the setting treatment is conducted by using a heating medium in-the vapor phase, low pressure steam is particularly applicable.

Although the process of this invention is particularly applicable to the treatment of fibers and yarns spun from vinyl resins made by the conjoint polymerization of a vinyl halide with a vinyl ester of an aliphatic acidf'and containing, preferably, between 70% and 95% of vlnvl'halide in the polymer, the invention is also applicable to the treatment of filaments and yarns made irom other water-insoluble vinyl resins having high average macromolecular weight, preferably in excess of about 15,000. Y

The term "yarn" is employed in the claims to designate an individual filament, as well as to designate the usual thread or the like formed by twisting together a plurality of such'filaments in well known manner.

Many modifications will be app rent to those skilled in the art, and the invention should not be limited other than as defined by the appended claims.

I claim:

1. Method for simultaneously setting and flexing stretched yarnmade from water-insoluble vinyl resins, which comprises passing the prestretched yarn continuously, while under tension to maintain the stretch therein, over supports within a heated zone so that the yarn is caused to change direction of travel abruptly one or more times and at the same time is heated to a temperature below its softening point for a period of time sufilcient toset the stretch in the yarn so that the yarn does not appreciably contract lustre throughout.

2. Method for simultaneously setting and flexing stretched yarn made from vinyl resins having average macromolecular weights of at least about 15,000, which comprises passing the yarn con the stretch in the yarn so that the yarn does not .Dpreciabiy contract upon release of the tension, and to provide a soft yarn of uniform, texture, tenacity, elongation and lustre throughout.

3. Method for increasing the elongation characteristics of stretched yarn made from vinyl resins having average macromolecular weights of at least about 15,000, which comprises passing the yarn continuously, under tension, oversupports in contact with a heated inert-liquid medium so that the' yarn is caused to change direction of travel abruptly one or more times and at the same time is heated to a temperature below its softening point for a brief period of time sufficient tout the stretch in the yarn so that the yarn does not appreciably contract upon release of the tension, and to provide a soft yarn of uniform texture, tenacity, elongation and lustre throughout.

4. Method for simultaneously setting and flexing stretched yarn spun from vinyl resins having average macromolecular weights of at least 15,000, made by the conjoint polymerization of vinyl chloride with vinyl acetate, and containing between. about 70% and about 95% by weight of vinyl chloride in the polymer, which comprises passing the yarn continuously, under tension, over rollers in contact with a heated inert liquid so that the yarn is caused to change direction of travel abruptly one or more times and at the same time is-heated to a temperature below its softening point for a brief period of time sumcient to set the stretch in the yarn so'that the throughout. 7 5. Method for increasing the elongation characteristics of stretched yarn spun from vinyl resins having average macromolecular weights of at least 15,000, made by the conjoint polymerization of vinyl chloride with vinyl acetate, and containing between about 70% and about 95% by weight of vinyl chloride in the polymer, which comprises passing the yarn continuously, under tension, over rollers in contact with a heated inert liquid so that the yarn is caused to change direction of travel abruptly one or more times and at the same time is heated to a temperature below its softening point for a brief period of time sufficient to set the stretch in the yarn so that the yarn does not appreciably contract upon release of the tension, and to provide a soft yarn of uniform texture, tenacity, elongation and lustre throughout.

' upon release of the tension, and to provide a soft yarn of uniform texture, tenacity, elongation and 6. In a method of setting and flexing stretched yarn made from water-insoluble vinyl resins, the

improvement comprising the steps of setting such a pre-stretched yarn by passing said yarn conlow the softening point of the yarn, to briefly expose said yarn to heat in said zone, and simultaneously flexing such set yarn, thereby producing a continuous yarn having substantially uniform texture, tenacity,

' throughout.

7. A continuous method of simultaneously setting and flexing pre-stretched yarn made from water-insoluble vinyl resins, which comprises passing successive portions of such stretched yarn through a heating zone maintained at a selected elevated temperature, and briefly exposing such yarn while in said zone to a temperature somewhat below its softening point while concurlustre and elongation rently flexing said yarn, thereby stabilizing the tenacity, shrinkage and elongation characteristics of such yarn, and improving the texture and lustre of the yarn.

- 8. Method for increasing the elongation characteristics of stretched yarn made from a vinyl resin produced by the conjoint polymerization or a vinyl halide with a vinyl ester of an aliphatic acid, which resin contains between about 70% and about 95% by weight of the halide in the polymer and has an average macromolecular weight of at least about 15,000, which comprises assaasa 

